Subterranean formations are regularly explored and exploited for resources through various drilling and extraction techniques. When trying to recover hydrocarbon resources from a subterranean formation, a well is typically drilled in the ground and then completed such that the hydrocarbon bearing portion of the formation is allowed access to the production tubing. One typical means of achieving this objective is first drilling the production zone and lining it with a casing. The casing is then perforated at certain points and the surrounding subterranean formation is fractured to allow the hydrocarbons to flow from the formation into the well.
The leakage of the reservoir fluids into the wellbore during such perforation operations is of substantial concern. Leakage is also a concern during other completion operations, such as workover operations. To maintain the hydrostatic integrity of the wellbore and reduce formation damage during these operations, fluid loss agents can be utilized. This fluid loss agent can temporarily seal the reservoir, allowing for well control during completion operations. Fluid loss agents often comprise a brine and a gelling agent. The gelling agent may be a biopolymer-based gellable agent (e.g., guar- and cellulose-based treatment agents and the like), a synthetic gellable polymer or another suitable gelling agent.
In many cases, fluid loss agents can be utilized in a gelled state when performing a treatment operation. For example, in a fracturing operation, a treatment fluid can be gelled to increase its viscosity and improve its ability to carry a proppant or other particulate material. In other cases, the gelling can be delayed so that the complete gelled state is not achieved until the fluid loss agent is at a desired location where it is used to temporarily divert or block the flow of fluids within at least a portion of a subterranean formation. In this latter case, the fluid loss agent being introduced into the wellbore is typically referred to as a “fluid loss pill”.
One problem associated with the use of fluid loss pills is that they can leak small amounts of fluids into the formation during the hold off period. These fluids leaked into the formation can alter the wettability of the formation, which may result in lower recovery rates from the well upon completion. They can decrease the reservoir permeability, which results in lower hydrocarbon recovery factors. Accordingly, methods of applying fluid loss pills without adversely affecting production are of substantial interest.